1. Field of the Invention
This invention relates to termination apparatus for use with elongate heaters in hazardous environments.
2. Introduction to the Invention
Elongate heaters of various kinds are known. They include both parallel cut-to-length heaters, for example self-regulating conductive polymer strip heaters, zone heaters and mineral-insulated cables. When such heaters are to be used in hazardous environments (where regulations require compliance with stringent precautions to prevent sparks or flames which could cause explosion or ignition of gases in the surrounding atmosphere), they are usually provided with an outer metal sheath, which may be corrugated to provide a degree of flexibility. Within the junction boxes in which the heater is terminated, the metal sheath is removed so that connection to the heater can be made. The heater enters the junction box through an entry port, which is of course somewhat larger than the cross-section of the heater. Regulations require the the entry port should be sealed in some way which prevents flames generated within the junction box from passing through the entry port to the atmosphere surrounding the junction box. Compliance with these regulations has proved to be difficult and expensive, due at least in part to the fact that the metal sheath does not have a completely regular cross-section, especially when it is corrugated, so that it is not possible to preform a grommet which conforms sufficiently closely to the sheath to provide the required flame control.